21690545978 has 8 divisors (see below), whose sum is σ = 32546457300. Its totient is φ = 10841726880.

The previous prime is 21690545963. The next prime is 21690545993. The reversal of 21690545978 is 87954509612.

It is an interprime number because it is at equal distance from previous prime (21690545963) and next prime (21690545993).

It can be written as a sum of positive squares in 2 ways, for example, as 14217462169 + 7473083809 = 119237^2 + 86447^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1765403 + ... + 1777646.

Almost surely, 2^21690545978 is an apocalyptic number.

21690545978 is a deficient number, since it is larger than the sum of its proper divisors (10855911322).

21690545978 is a wasteful number, since it uses less digits than its factorization.

21690545978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3546112.

The product of its (nonzero) digits is 5443200, while the sum is 56.

The spelling of 21690545978 in words is "twenty-one billion, six hundred ninety million, five hundred forty-five thousand, nine hundred seventy-eight".