61821921 has 16 divisors (see below), whose sum is σ = 94316544. Its totient is φ = 35284944.

The previous prime is 61821889. The next prime is 61821923. The reversal of 61821921 is 12912816.

It is a happy number.

It is not a de Polignac number, because 61821921 - 2⁵ = 61821889 is a prime.

It is a super-2 number, since 2×61821921² = 7643899832260482, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (61821923) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 28936 + ... + 30998.

It is an arithmetic number, because the mean of its divisors is an integer number (5894784).

Almost surely, 2^61821921 is an apocalyptic number.

It is an amenable number.

61821921 is a deficient number, since it is larger than the sum of its proper divisors (32494623).

61821921 is a wasteful number, since it uses less digits than its factorization.

61821921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3500.

The product of its digits is 1728, while the sum is 30.

The square root of 61821921 is about 7862.6917146738. The cubic root of 61821921 is about 395.4098635160.

The spelling of 61821921 in words is "sixty-one million, eight hundred twenty-one thousand, nine hundred twenty-one".