64215981 has 12 divisors (see below), whose sum is σ = 94277820. Its totient is φ = 42108480.

The previous prime is 64215967. The next prime is 64215997. The reversal of 64215981 is 18951246.

64215981 is a `hidden beast` number, since 64 + 2 + 1 + 598 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 30969225 + 33246756 = 5565^2 + 5766^2 .

It is not a de Polignac number, because 64215981 - 2¹⁰ = 64214957 is a prime.

It is a super-2 number, since 2×64215981² = 8247384431584722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (64215961) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 57936 + ... + 59033.

It is an arithmetic number, because the mean of its divisors is an integer number (7856485).

Almost surely, 2^64215981 is an apocalyptic number.

64215981 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

64215981 is a deficient number, since it is larger than the sum of its proper divisors (30061839).

64215981 is a wasteful number, since it uses less digits than its factorization.

64215981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117036 (or 117033 counting only the distinct ones).

The product of its digits is 17280, while the sum is 36.

The square root of 64215981 is about 8013.4874430550. The cubic root of 64215981 is about 400.4494552026.

The spelling of 64215981 in words is "sixty-four million, two hundred fifteen thousand, nine hundred eighty-one".