21261604656610 has 32 divisors (see below), whose sum is σ = 38903862997872. Its totient is φ = 8364020858880.

The previous prime is 21261604656553. The next prime is 21261604656623. The reversal of 21261604656610 is 1665640616212.

It can be written as a sum of positive squares in 8 ways, for example, as 1906893095409 + 19354711561201 = 1380903^2 + 4399399^2 .

It is a super-3 number, since 3×21261604656610³ (a number of 41 digits) contains 333 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1758114 + ... + 6753826.

Almost surely, 2^{21261604656610} is an apocalyptic number.

21261604656610 is a deficient number, since it is larger than the sum of its proper divisors (17642258341262).

21261604656610 is a wasteful number, since it uses less digits than its factorization.

21261604656610 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5002758.

The product of its (nonzero) digits is 622080, while the sum is 46.

The spelling of 21261604656610 in words is "twenty-one trillion, two hundred sixty-one billion, six hundred four million, six hundred fifty-six thousand, six hundred ten".